(Reuters) - A judge in the election battleground state of Pennsylvania on Wednesday rejected an effort to block the state's voter identification law, which civil rights groups argued discriminates against minority voters.

Pennsylvania, a major electoral prize in the November 6 presidential election between Democratic President Barack Obama and Republican challenger Mitt Romney, is one of 11 states to pass laws since 2010 requiring voters to show some form of legal identification. The laws have become a contentious issue ahead of the November 6 elections.